Agree with all the above.
I deal with the Capital sector which takes you from Avant or May to BPK. I won't add too much apart from the 5000' bit is a symptom of how the TMA has expanded and routes and airfields have grown around Heathrow. The relatively long period at 5000' on the 'full route' is the only way to safely incorporate the Luton traffic through the rather complex airspace(!)
This ends at 'gate' through which all the standard routed arrivals are fed to Luton APC.